Heat-resistant metallic materials for use in high-temperature gas-cooled reactors are nickel- or iron-base, solid-solution-strengthened, or age-hardened alloys. To control the material behavior and to adapt it to realistic load conditions, they have to be tested and characterized. During recent years, interference layer metallography has become an independent characterization procedure as well as an outstanding method for sample preparation for the application of quantitative image analysis to these refractory alloys. The special problems of characterization of nickel- and iron-base alloys that can now be solved by interference layer metallography and its physical backround are reported. Chromatic contrasting and the subsequent phase analysis by way of the example of three common alloys are discussed. Finally, the optimization of interference layer metallography for application in quantitative image analysis is described.